Prostate cancer afflicts over 200,000 new patients, with a disproportionately large number of African-Americans, and causes 41,800 deaths(1) each year. Brachytherapy is an effective process for prostate cancer treatment,(2) and is being selected by a rapidly increasing proportion of patients. Current generation brachytherapy seeds consist either of 125I or (103)Pd encapsulated in titanium shells. Each seed is designed to resemble a point source with an isotropic distribution. In reality, the dose anisotropy is as much as 60%(3). The seeds are often not delivered with precision, end up misaligned, and are subject to migration, leading to the possibility of inadequate dose to the tumor. The method of manufacturing seeds is rudimentary, inefficient, labor intensive, and costly. This Phase II application expands the highly successful work on the production, evaluation, and dosimetry of linear sources: source manufacturing will be scaled up; a new delivery system will be introduced; the dosimetry of the wires will be expanded to include a dose atlas and improved treatment planning". The information necessary to establish equivalence of the wires to seeds will be submitted to the FDA; the safety of the linear sources will be evaluated in an animal model and in a clinical study. PROPOSED COMMERCIAL APPLICATIONS: Penetration of the market for the brachytherapy modality for treatment of prostate cancer is expected to increase from the current 10-15% to over 50% in 5 years.(4) Interstitial brachytherapy by placement of seeds is FDA approved, well accepted, and covered by Medicare and other reimbursement plans. The linear sources proposed here for further development are compatible, yet superior in many ways to seeds. By proving this superiority to seeds in a clinical setting, together with the expected economic advantages, early commercial success of the linear sources will readily be established. In time, the linear sources are expected to replace seeds in the prostate brachytherapy market.